1. Field of the Invention
The present invention relates to a contact displacement meter using a contact.
2. Description of Related Art
A contact displacement meter has a contact which is linearly movable in one direction while being brought into contact with the surface of an object (e.g., see JP 2009-236498 A). A contact displacement meter of JP 2009-236498 A includes a light-emitting element, a line sensor, and a moving scale. The moving scale is connected to a contact. A predetermined pattern is arrayed in the moving scale along a direction in which the contact is movable.
Light emitted from the light-emitting element is turned into substantially parallel light by passing through a collimator lens, and the light then passes through the moving scale and is applied to a line sensor. Based on a light reception signal read by the line sensor, displacement of the contact is calculated.
In JP 2009-236498 A, it is possible to calculate displacement of the contact in units (sub-pixel units) smaller than a pixel of the line sensor by use of interference of the light having passed through the moving scale. However, an optical element for collimating light, such as the collimator lens, needs to be provided between the light-emitting element and the moving scale, and thus it is difficult to reduce the size of the contact displacement meter in a direction orthogonal to the moving direction of the contact.